Welcome to the PSA Forum, you are sure to get many opinions here and some helpful advice as well. I just added REL T5i (Black) subs to my den system. I am currently running them in with about 17 hours of break-in on them. I set-up a REL break in playlist on Tidal so that I could set it and forget it. Let me know if you’d like me to share it, and I’ll forward it in a PM. Out of the box they were pretty stiff, and the run-in seems to be doing its magic. It’s also a good way to ensure there isn’t a problem with them. I intend to let them run 24 hours straight and then tighten the driver mounting.
My den is similar in size to your room being about 14’x16’ with 10’ ceilings. Flooring is hardwood oak with carpet over it. Walls and ceiling are plaster. I replaced my dreadful AV system with new digital/streaming oriented system. The focus was on good sound with ease of use, more for casual listening while relaxing. In this situation I prefer a simple, system approach, (read minimize the number of boxes). The system is centered around Aerial Acoustics 5T speakers. They are driven by a Hegel H120 with streaming provided by a BlueSound Node 2i. CDs are played via a Cambridge CXC V. 2 transport which feeds the Hegel via a BJC coax.
The Aerial Acoustics are right sized for my room and listening tastes. Bass on them is reasonable down to the low 50hz range. I was curious if adding a modest subwoofer would flesh out the bottom end slightly with out overdriving my den. The latter being my primary concern, as I prefer an over damped versus wooly bottom end. In a room this size ultimate low end frequency extension was not a goal, nor is it realistic. I’m not into “bass drama”. My listening preferences lean towards innovative jazz with properly reproduced double bass, thus flat response down to 42hz is the goal.
As the T5i is still breaking in I will withhold my opinion.
Which woofer/subwoofer is right for you? Well, only you can say. Partnering it to the room is fundamental, everything else will be secondary. Seems to me you are on the right path. When I heard the T7i and the T9i I thought they were too much bass for my room. If your goal is flat response down to 20hz this is not the answer. If you seek to flesh out the bottom end down to 38 hz, mol, the TZero may well be. Sorry to say looks as though I got one of the last immediately available black REL T5i’s. I did not audition or consider the TZero. Eagerly anticipating your sharing of the integration of the TZero with your system and room.
BTW due to the ongoing snow storm here I am listening to the sT5i break in this morning with Kraftwerk’s Autobahn, followed by YELLO.